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© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-1 Wireless Fundamentals Examining Wireless Media Access

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  • 1. Wireless Fundamentals Examining Wireless Media Access

2. Sending a Frame 3. Sending a Frame (Cont.) 4. Sending a Frame (Cont.) 5. After a Frame Is Sent 6. 802.11 Frame Shape 7. Frame Types

    • Management:
      • Beacon, probe request, probe response
      • Authentication request, authentication response
      • Association request, association response
      • Deauthentication, reassociation request, reassociation response
      • Announcement Traffic Indication Message (ATIM)

8. Frame Types (Cont.)

    • Control:
      • Request to send (RTS), clear to send (CTS), acknowledgment (ACK),
      • Power Save Poll (PS-Poll),
    • Data:
      • Simple data
      • Null function (empty frame)

9. 802.11 Frame Speeds 10. Discovering the Network (Mgmt Frames) 11. Connecting (Mgmt Frames) 12. Staying Connected (Mgmt Frames) 13. Control Frames

  • ACK is used after each frame.

RTS and CTS are used in 802.11b and g mixed cells and in hidden node situations. 14. WMM Enhancement 15. Power Save Mode 16. Summary

    • Sending a frame requires a timing and acknowledgment system that is based on CSMA/CA.
    • 802.11 frames have a specific shape with headers containing specific information and different parts that are sent at different speeds.
    • Beacons and probes help discover the network.
    • Authentication and association frames are used to join the cell.
    • Some other management frames may be used while the client is connected.
    • Control frames improve the communication framework by allowing special messages in specific cases, such as RTS and CTS or PCF.
    • Some stations may use the power save mode to increase battery time, which means there must be specific exchanges with the AP.